The present invention relates to a word processor in the Japanese language or another language such as English, and more particularly to a document creating and editing apparatus which has an enhanced editing performance.
In order to enhance the editing performance of a word processor, word processors furnished with various functions have recently been proposed. There has been known, for example, a page administration function by which a page to be seen, such as the previous page or next page of a document displayed on a display screen, can be immediately called and displayed. In the editing of a document, the document proofreading or editing performance is very important for making up the format of the document and determining the arrangement of an expression. In this regard, there has been the problem that when a character string is subjected to an alteration such as correction, addition or deletion, the arrangement of an expression on the next page may change greatly.
The above problem will be explained with reference to FIGS. 1A and 1B. In these figures, numerals 1, 2 and 3 designate first to third pages on printed out paper or on the display screen of a CRT or the like. Symbol 1a denotes the boundary between the first page and the second page, and symbol 2a the boundary between the second page and the third page. It is now assumed that, as shown in FIG. 1A, a sentence ` ` (`The editing of a document has been executed.`) is written at the last line and the second-last line of the first page 1, sentences 2.sub.1, 2.sub.2, 2.sub.3 and 2.sub.4 of four lines being written on the second page 2, sentences 3.sub.1 and 3.sub.2 of two lines being written on the third page 3. By way of example, it is considered that a cursor position indicated by ` ` (`sentence`) has five characters (` ` (`inserting a character string`) added thereto. Then, as shown in FIG. 1B, a character and a punctuation mark ` ` (`hiragana "ta" and a period`) overflow the last line of the first page 1 to come to the first line of the second page 2, and the sentences 2.sub.1, 2.sub.2 and 2.sub.3 having been at the first to third lines are still included in the second page 2, but the sentence 2.sub.4 of the fourth line shifts to the first line of the third page 3. That is, the proofreading such as the addition or deletion of characters into or from a sentence results in changing the boundaries of pages from those shown in FIG. 1A before the editing or proofreading, and the arrayal of characters on each page behind the proofread position is discrepant by at least one line as compared with the state before the proofreading. Therefore, the positions of the same character string before and after the editing or proofreading differ in page and line. This has led to the disadvantage that a character string is difficult to find when editing is performed later.
Further, there has been known another editing system wherein a document is edited in single page unit. According to this system, in a case where a cursor position ` ` (`sentence`) in a sentence ` ` (`The editing of a document has been executed.`) on a first page 1 shown in FIG. 2A has ` ` (`inserting a character string`) added thereto as shown in FIG. 2B, the first page 1 expands to absorb increase in the number of lines and to exert no influence on a second page 2 and a third page 3, and an operation called page make-up is finally performed to fix true boundaries as shown in FIG. 2C. This system, however, has had the disadvantage that how the result of the editing has changed as the whole document cannot be acknowledged instantly.
Moreover, the systems shown in FIGS. 1A and 1B and in FIGS. 2A to 2C have had the drawback that, once the editing has been executed, the document cannot be restored into its original state.